This research proposal is designed to study changes occurring at the surfaces of neuronal processes (axons) and their satellite cells (Schwann cells and oligodendrocytes) during development, degeneration and regeneration by means of electron opaque stains which bind to surface mucosubstances of the cell coat. Utilizing alcian blue, ruthenium red, colloidal iron, lanthanum hydroxide, phosphotungstic acid and periodic acid-silver methenamine, studies will be done on myelinogenesis in the peripheral nerve of the developing animal, regeneration of peripheral nerve following a crush injury, degenerative and regenerative stages of experimental allergic neuritis and vincristine neuropathy. In the central nervous system similar studies will be done on regeneration in the posterior column of the spinal cord following cordotomy and the degenerative and regenerative stages of experimental allergic encephalomyelitis. The staining properties of the cell surfaces will be further characterized by their response to the enzymatic actions of hyaluronidase, neuraminidase trypsin, pepsin and protease. These experiments are designed to alter the cell coat in various ways so as to yield information regarding its role in axon- satellite cell relationships and, as a consequence, in axonal regeneration and myelin formation.